1. Field of the Invention
The present invention relates to a liquid spreading device for spreading liquid over a target surface of a predetermined member. Also, the invention relates to a fixing device for fixing an unfixed toner image, which is carried on a recording sheet, onto the recording sheet, and particularly a fixing device provided with a rotating member having an outer peripheral surface to which liquid such as oil is applied for increasing releasability from toner.
2. Description of the Background Art
In electrophotographic image forming apparatuses such as a copying machine and a printer, a toner image is transferred onto a recording sheet (e.g., paper sheet) by an electrophotographic image forming process.
The toner image transferred onto the recording sheet is merely carried on the recording sheet in an initial stage, and therefore the toner image will be usually fixed onto the recording sheet by a fixing device.
The fixing device generally has two fixing rollers opposed to each other. Usually, a heat source is provided for one of the fixing rollers for heating the roller. Usually, these two fixing rollers are pressed to each other.
When fixing the unfixed toner image onto the recording sheet, the recording sheet is moved between these fixing rollers for applying a heat and a pressure to the toner image on the recording sheet so that the toner image is fixed.
For preventing the transfer of the toner from the recording sheet to the fixing roller, which is in contact with the toner image on the recording sheet, when the recording sheet is moved between the fixing rollers, such a manner has been proposed, in which oil is applied and spread over this fixing roller. The oil applied to the fixing roller increases the releasability of the toner from the fixing roller, and in other words, promotes releasing of the toner from the fixing roller so that transfer of the toner onto the fixing roller can be suppressed.
When the oil is applied to the fixing roller, the fixing device is usually provided with an oil spreading roller in contact with the fixing roller. The oil supplied to the oil spreading roller is transported in accordance with rotation of the spreading roller, and thereby the oil is applied to and spread over the fixing roller.
If an excessively large amount of oil were applied to the fixing roller, disadvantages such as smearing of the recording sheet with the oil might occur. For preventing such disadvantages, a blade pressed against the fixing roller is employed for scraping off excessive oil. In some structures, the blade is pressed against the oil spreading roller.
In the above structure wherein the blade is pressed against the fixing roller for scraping off the oil, however, it is necessary to change the pressure or pressing force of the blade if the amount of oil left on the fixing roller is to be changed. For this purpose, a mechanical mechanism is required for changing the pressing force of the blade, which complicates the fixing device and increases the whole size and the cost. This is also true in the case where the blade is pressed against the oil spreading roller.